I don't think the 4770 is Devil's Canyon. I believe that's only the 4690K and 4790k.
If you get a 4790K, you're probably not going to get much out of it from overclocking, as it comes from the factory with a max turbo of 4.4ghz. There seems to be little point in having a Z-series chipset with that particular chip, to me.
The clockspeed difference is ~12%. That's probably less than what's perceivable. Personally, I wouldn't bother.